Note If this server is a stand−alone server, you can skip this section. If this server is your first domain controller, read and complete the hands−on part of this section. If you dont complete this task, based on the way were going to do things in this book, your Exchange 2003 server will not become a part of your DNS domain and will thus not be available to users trying to open their mailboxes, or to other servers trying to send mail to your Exchange server.
In Chapter 8, youll install a Windows 2003 stand−alone server and then install Exchange Server 2003 on it. Before installing Windows 2003 on your soon−to−be Exchange server, you must set up your domain so that the new server can easily enter your network. You can do that right here using a special capability of DHCP called address reservation.
Address reservation allows DHCP to automatically allocate the same IP address to a server or workstation each time the computers address lease expires. That way, your Exchange server will always have the same IP address. And, everything is done on the DHCP server side. You dont have to touch your soon−to−be
Exchange 2003 server, which is, of course, a DHCP client in this case.
Address reservations are important especially when outside servers need to find your Exchange servers address. It takes a few minutes to a few days for a new DNS entry to propagate across the Internet. So, if your Exchange servers IP address changed every day, servers trying to send mail to the server could be out of touch for an unacceptable period of time.
You could assign a hard IP address to your new server. However, that would mean you have to go through hell and high water any time you needed to change that address. With a DHCP address reservation, all you have to do is remove the reservation and run a program called IPCONFIG.EXE on the server with the lease to release the old address. At that point, youve reclaimed the address and can use it for any other purpose. Okay, lets get going. I assume here that you have access to the Administrator account for your domain controller. If you dont, someone else will have to do the following. Go to your domain controller. As you might remember, my domain controller is called BG01. Log in as Administrator.
Heres how to set up a DHCP reservation. Start up your Microsoft Management Console (MMC), and click open the DHCP container until it looks like the one in Figure 7.32. Now, do what the right pane of the Reservations subcontainer says: Select New Reservation from the Action menu.
Figure 7.32: Ready to create a new DHCP IP address reservation using the Microsoft Management Console DHCP snap−in
This brings up the New Reservation dialog box shown in Figure 7.33. Give the reservation a name, and enter the IP address that you want to assign to your new server.
Figure 7.33: Creating a new DHCP IP address reservation
Next type in the Media Access Control (MAC) address of the network adapter to which you want to assign the address. The MAC address is a unique address thats burned into each network adapter when it is
manufactured. An international standard ensures that no network adapter, no matter who makes it, will have the same MAC address as any other network adapter. Thats how DHCP knows which machine to give the reserved address to when contacted by a bevy of IP addresshungry computers.
How do you find out the MAC address of a network adapter? Good question. For some adapters, the MAC address is actually on a little sticker on the adapter or on the box that the adapter came in. Additionally, most adapters come with a configuration utility that can be run under MS DOS. Among other things, the utility tells you the MAC address of the adapter. For example, 3Coms 3C90x line of adapters comes with a program called 3C90XCFG.EXE. When you boot up under DOS (say, with a Windows 98 boot disk) and run 3C90XCFG.EXE, the first screen shows you the MAC address. If, by some chance, before you install
Windows 2003 on the computer, it is up and running under Windows 2003 (or NT 4), you can open a command prompt and type IPCONFIG ALL | MORE. The MAC address is listed as the physical address, usually on the first screen right under the description of the adapter itself. Copy the address exactly as you see it. You dont have to enter the dashes.
It might seem like a heck of a lot of work to find an adapters MAC address. Actually, its quite simple, and when you see how automatic fixed address assignment simplifies network management, youll agree that its worth a little extra work to obtain the address.
Next, if you want, you can enter some text in the New Reservation boxs Description field. Leave Supported Types set to Both. When youre done, click Add. When the address has been created, your Reservations container should look something like the one in Figure 7.34. The DNS servers information that you set by the Configure Your Server Wizard is inherited by the reservation (see the right pane in Figure 7.34). If you add new options information, it will also be inherited by the server.
Figure 7.34: The newly created IP address reservation, complete with inherited DNS server information Thats it. Your DHCP server is configured to provide your Exchange server a fixed IP address when you install it in the next chapter. And, remember, because Dynamic DNS is enabled, your server will also be
automatically registered in your domain DNS. Thats about as easy as it gets.
Getting the Most from DHCP
You can use DHCP address reservations for any computer that is part of your network. This includes most domain controllers. The only computers on your network that must absolutely have fixed addresses assigned to their network adapters when Windows Server 2003 is installed are domain controllers that serve as DHCP servers. For safety, you should be sure that there are at least two DHCP servers on any network segment. You dont want your network to be without an IP address server if your one and only DHCP server fails. When you set up additional DHCP servers, remember that, except for reserved addresses, the specific IP addresses in each servers address pool(s) must be unique.
If you wish, you can set up a new DHCP scope for external Internet addresses. This will let you automatically assign addresses to computers connected to a WAN. Again, dont use DHCP and reservations for servers that provide DHCP services. Be sure to set a reservation for each address so that IP addresses arent leased to just any computer that hits your DHCP server. Reserve each external IP address, even if youre not ready to use it. Use a bogus MAC address, if you dont have the MAC addresses of the network adapters you plan to use for external connections. The MAC address should be 12 characters long and can consist of the letters AF and/or
the numerals 09. For safety, use bogus MAC addresses beginning with 99. It will be a long time, if ever, before MAC addresses that begin with 99 show up. To see the current assignment of MAC address prefixes to network adapter manufacturers, check out http://standards.ieee.org/regauth/oui/oui.txt.